A coaxial line-to-waveguide adapter (CWA) is a device, in an antenna feed structure, used for connecting a waveguide and a coaxial cable. An orthogonal coaxial line-to-waveguide adapter becomes a most commonly used type of coaxial line-to-waveguide adapter because of a simple design of the orthogonal coaxial line-to-waveguide adapter. As shown in FIG. 1-a, FIG. 1-a is a front view of an existing orthogonal coaxial line-to-waveguide adapter, and FIG. 1-b is a left view, corresponding to FIG. 1-a, of an orthogonal coaxial line-to-waveguide adapter. A horizontal section of FIG. 1-a or FIG. 1-b is a waveguide connection component 101 of the coaxial line-to-waveguide adapter, and a vertical section thereof is a coaxial external conductor 102. The waveguide connection component 101 is essentially a waveguide. When the orthogonal coaxial line-to-waveguide adapter is used, the waveguide connection component 101 is connected to a waveguide, and one end of the coaxial external conductor 102 is connected to a coaxial cable. In FIG. 1-a and FIG. 1-b, a dimension of a wide side of the waveguide connection component 101 is a (FIG. 1-a), and a dimension of a narrow side of the waveguide connection component 101 is b. A coaxial internal conductor 103 of the orthogonal coaxial line-to-waveguide adapter is generally inserted, at the center of a wide side of the waveguide connection component 101, into the wide side of the waveguide connection component 101 in a form of a probe. The other end of the coaxial external conductor 102 is connected to a wall of the waveguide connection component 101 (by means of, for example, welding or connecting by using a screw). Impedance matching can be implemented theoretically by adjusting a depth d at which the coaxial internal conductor 103 is inserted into the waveguide connection component 101 and a distance 1 (FIG. 1-a) between the coaxial internal conductor 103 and a waveguide short-circuit end of the waveguide connection component 101. However, the foregoing method for implementing impedance matching can well implement impedance matching only at one frequency (a center frequency of a frequency band is usually selected), but generally, operating bandwidth of a system is relatively large, and therefore when considered bandwidth is relatively large, flatness of a reflection coefficient in an entire frequency band is still relatively poor, and for some systems that have a high requirement on in-band flatness, such unsatisfactory flatness of a reflection coefficient brings serious impact.
For the foregoing technical problem, a solution provided in the prior art is designing a coaxial line-to-waveguide adapter for varied frequency bands, and another solution is adding an impedance matcher on the basis of an existing coaxial line-to-waveguide adapter. For the solution of designing a coaxial line-to-waveguide adapter for varied frequency bands, costs of the solution are high, and for a bandwidth system, multiple devices are needed to implement one system, thereby causing more inconvenience. For the solution of adding an impedance matcher, design of the solution is complex, and system matching is difficult to implement within a relatively wide frequency band.